This project examines the mechanisms of matrix and trophic coupling within the neurovascular unit. We hypothesize that outside-in integrin signaling allows cerebral endothelium to secrete growth factors (e.g. brain derived neurotrophic factor, BDNF) that provide trophic support for neuronal health. In diseased conditions, oxidative stress and disruption of matrix-cell interactions by extracellular proteases (e.g. matrix metalloproteinases, MMPs) decouple these growth factor signals in the neurovascular unit. We will test this overall hypothesis using cell culture and whole animal models in 4 specific aims. In Aim 1, we will test the idea that oxidative stress (nitric oxide, oxy-LDL, A(3)can suppress BDNF production in cerebral endothelial cells even in the absence of overt cell death. We use conditoned media transfer experiments to show that BDNF from endothelial cells can protect neurons from excitotoxic, oxidative and apoptotic insults. In Aim 2, we examine pathways that link beta-1 integrin and integrin linked kinase (ILK) with BDNF secretion in cerebral endothelial cells. Integrin activating or blocking antibodies, ILK mutants and pharmacologic inhibitors are used to document these pathways. Recombinant MMPs or cells from MMP null mice will be used to investigate how extracellular matrix proteolysis disrupts integrin homeostasis and decreases endothelial BDNF. In Aim 3, we test the importance of endothelial-to-neuron BDNF pathways using 3 in vivo mouse models: focal cerebral ischemia, aging, and the APPswe/PS1dE9 transgenic mouse model of cerebral amyloidosis. We will use a combination of in vivo 2-photon imaging, laser capture microdissection, and standard immunohistochemistry to see whether areas of disrupted neurovascular matrix and reduced endothelial BDNF coincide with neuronal dysfunction and death in vivo. In Aim 4, we will directly manipulate endothelial BDNF expression by delivering the BDNF gene encased in TAT-liposomes into mouse brains in vivo. We hypothesize that upregulating endothelial BDNF may be sufficient for neuroprotection in models of brain injury. We will interact closely with the Neurovascular Coupling Core to image neurovascular responses in all our animal models in vivo. Taken together, these data should support our basic hypothesis that cerebral endothelial cells are not just inert conduits for blood flow, but also play a key role in matrix and trophic coupling for the neuron.